A MULTI-PROXY CHARACTERIZATION OF THE HOLOCENE DRY PERIOD FOR TWO SITES FROM SOUTH-CENTRAL MINNESOTA
GEISS, Christoph E., Department of Physics, Trinity College, Mc Cook 105, 300 Summit St, Hartford, CT 06106, christoph.geiss@trincoll.edu, CAMILL, Phil, Dept. of Biology, Carleton College, 1 North College Street, Northfield, MN 55057, and UMBANHOWAR, Charles E. Jr, Dept. of Biology, St. Olaf College, 1520 St. Olaf Ave, Northfield, MN 55057

Kimble Pond and Sharkey Lake are two small glacial lakes in south-central Minnesota that provide a continuous high-resolution record of paleoclimate throughout the Holocene. In both lakes sediment-magnetic parameters (magnetic susceptibility, ARM/IRM, hysteresis parameters) show an increase in coarse-grained magnetic minerals during the early to mid-Holocene dry period between 4000 - 9000 yrs. B.P. (cal. 14C), and large changes in these parameters suggest highly variable lake conditions during this period. The drier conditions are confirmed by low-resolution pollen analyses, which show a decrease in the ratio of arboreal / non-arboreal pollen. Lake productivity, as inferred by biogenic silica analyses, was high during this dry interval. Charcoal concentrations are low throughout most of the Holocene, but show a significant peak between 3000 - 4000 yrs B.P., indicating increased fire frequency when increased moisture availability led to more abundant fuel supply. A comparison of the various paleo-climate proxies shows that sedimentological and magnetic proxies tend to respond rapidly to changing watershed conditions, while pollen and charcoal analyses present a smoother record and are likely to indicate regional changes.

Northeastern Section - 37th Annual Meeting (March 25-27, 2002)
General Information for this Meeting
Session No. 19
Holocene Climate and Lakes (Posters)
Sheraton Springfield: Ballroom North
8:00 AM-12:00 PM, Tuesday, March 26, 2002
 

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